The present invention relates to a method of detecting reverse rotation of a direct-current (DC) motor by using the back electromotive force (EMF), wherein an EMF extract circuit is exploited to extract the EMF, and then a voltage comparator is exploited to measure this EMF. If it is higher than a threshold voltage, a signal is outputted to let a controller for controlling the DC motor stop working so as to prevent the reverse rotation of the DC motor.
Conventional ways of judging whether a DC motor brakes to a halt generally use attached sensors such as optical interruptor or special mechanisms to rub the rotating shaft of the motor so as to judge whether the brakeage of the motor is finished. Therefore, additional sensors, special mechanisms, or circuits of higher price are required so that the cost is high.
The present invention aims to resolve the above problem.
The primary object of the present invention is to provide a method of detecting reverse rotation of a DC motor by using the back EMF, wherein the back EMF of the DC motor is detected to judge whether the brakeage of the motor is finished. A simple electronic circuit can be exploited to accomplish this work effectively. No additional sensors are required so that the cost can be reduced.